1. Field of the Invention
The present invention relates to a rotary piston engine, and more particularly, a fuel supply system for the stratified combustion rotary piston engine of the type described in Japanese Pat. application No. 71426/74 filed on June 24, 1974 by the same assignee as the present invention.
2. Description of the Prior Art
In the so-called Wankel-type rotary piston engine which comprises a casing composed of a rotor housing having a trochoidal inner peripheral surface and side housings which close opposite sides of said rotor housing and a polygonal rotor adapted to rotate eccentrically in said casing with its apex portions sliding over said inner peripheral surface, the flame initiated from an ignition plug propagates very swiftly toward the leading side located at the rotational front side of the rotor due to the flow of the fuel-air mixture caused by the rotation of the rotor, however, the propagation of the flame toward the trailing side located at the rotational rear side of the rotor is difficult to achieve. Thus, there is a problem in that the fuel-air mixture is favourably combusted in the leading side whereas the combustion is incomplete in the trailing side which lowers the combustion efficiency with an increase in the fuel consumption while simultaneously increasing harmful uncombusted components such as HC and CO emitted in the exhaust gas. In order to solve this problem, the aforementioned Japanese Pat. application No. 71426/74 proposes to provide the rotary piston engine with a first intake port which opens in said trochoidal inner peripheral surface and a second intake port which opens in an inner surface of said side housing at a portion advanced from said first intake port with respect to the rotational direction of the rotor. A fuel-air mixture is supplied to said first intake port and only air is supplied to said second intake port, thereby accomplishing stratified charging such that the leading side portion of the combustion chamber where the combustion of the fuel-air mixture is relatively easily effected, is filled with a relatively rich fuel-air mixture, while the trailing side of the chamber where the combustion of the mixture is difficult to achieve is filled with only air. For use with this particular rotary piston engine, in order to supply a fuel-air mixture to said first intake port and only air to said second intake port, Japanese Pat. application No. 78721/74 filed on July 11, 1974 by the same assignee as the present invention has proposed a particular two-barrel type carburetor which comprises a first supply system including a Venturi, a main nozzle, a main jet, a float chamber, etc. and being adapted to supply a fuel-air mixture and a second supply system adapted to supply only air, said first and second supply systems further including first and second throttle valves respectively incorporated therein and interconnected with each other by a linkage mechanism.
However, it is relatively difficult to maintain the optimum air/fuel ratio throughout the entire operational region of the engine when the fuel-air mixture is generated by a carburetor such as the abovementioned type. In the abovementioned stratified combustion rotary piston engine, the overall air/fuel ratio is determined by the amount of fuel supplied through said first intake port (peripheral intake port) (Peri fuel) and the amount of air supplied through said first intake port (Peri air), the fuel and air being supplied as a fuel-air mixture, and the amount of air supplied through said second port (side port) (Side air) according to the following formula: ##EQU1##
Therefore, in addition to a substantial difficulty in controlling the air/fuel ratio at a desired value over the entire operational region in a conventional rotary piston engine, the present stratified combustion rotary piston engine further requires to control .alpha. in relation to .beta. thereby making it very difficult to maintain the overall air-fuel ratio at the optimum value throughout the entire operational region of the engine, if the fuel supply system depends upon the conventional carburetor system.